The invention relates to an adjustable cutting tool and is particularly but not exclusively, concerned with the cutting tool of the kind used on a boring bar in a lathe.

It has been proposed hitherto to provide an adjustable cutting tool comprising an elongate body including or arranged to carry a cutter element at one end, the body being axially adjustable, in use, in a bore in a tool holder by means of an internally screw threaded adjustment member engaging external screw threads on the body, a radial projection being provided on the body and engageable with part of the tool holder to inhibit rotation of the body in the bore. Typical examples of such tools are described in GB-A-2100152, GB-A-2089695, GB-A-2083387, GB-A- 1150515, GB-A-1145231 , GB-A-1076388, GB-A-1028096, US-A-4516889 and US-A-2537517.

During use, the adjustment member which is normally in the form of a graduated ring, can become damaged and it is necessary to provide a replacement. In order to do that, it is necessary to remove the adjustment member from the body of the tool.

The above references teach the use of a radial projection in the form of a key which engages a key- way to prevent rotation of the body. The key terminates radially outboard of the external screw- thread on the body which means that the adjustment member on the body cannot be removed therefrom by unscrewing it along the body away from the cutting end thereof. That arrangement is satisfactory where arrangement permits removal of the adjustment member past the cutting element. However, where the cutting element is of a substantial size, the cutting element is conventionally solid with the body. During manufacture, the adjustment member is screwed on to the body from the end opposite the cutting element and then the key is fixed to the body. On larger size tools the key is typically screwed in position and needs to be unscrewed if the adjustment member is to be removed. That is a tedious and time consuming operation. On smaller sizes two methods are conventionally used as follows:-

1. An accurate diametral slot is formed across the body and a key is brazed in position. With such an arrangement it is impossible to remove the adjustment member.

2. A dowel hole is accurately machined in the body and a dowel pin permanently fitted to form a key. Again it is impossible to remove the adjustment member in such a case.

Such tools are sold as complete assemblies and do not allow for the exchange of the adjustment member.

An object of the present invention is to provide an improved cutting tool in which the foregoing disadvantage is substantially reduced.

According to one aspect of the invention there is provided an adjustable cutting tool comprising an elongate body including or arranged to carry a cutting element, the body being axially adjustable, in use, in a bore in a tool holder by means of an internally screw-threaded adjustment member engaging external screw threads on the body, and a radial projection on the body engageable with part of the tool holder to inhibit rotation of the body in the bore, the radial projection extending outwardly for a distance which will permit the adjustment member to pass axially over the projection for removal from the body.

Such an arrangement is particularly useful in that the radial projection will no longer inhibit removal of the adjustment member in a direction away from the cutter element.

Preferably, the radial projection terminates at a position radially inboard of the root of the external screw thread.

The body may have a first section on which the external screw threads are formed, and a reduced diameter pilot portion intermediate the projection and the first' section.

The radial projection may be formed on an end of the body, e.g., an end of the pilot portion, opposite the cutting end.

Locking means are provided for locking the body in its adjusted position within the bore in the tool holder. The locking means may be in the form of a screw engagable with the tool holder and which preferably extends into a screw-threaded bore in the body.

The adjustment means may be in the form of a ring having one or more graduations thereon.

As well as using a dowel or a key in a diametral slot, it has also been proposed to upset the material of the body to form a radial projection which is undesirable as the upseting subsequently requires machining and can produce undesirable stresses in the body. It is proposed to provide an improved arrangement by forming an annular flange at or towards one end of the body which projects radially therefrom and subsequently removing diametrically opposed portions of the flange to form at least one radial projection. In that way, the interfitting of a dowel within a hole and a key within a slot is avoided and no upsetting of the body material is required.

According to a further aspect of the invention there is provided an adjustable cutting tool having an elongate body including a radial projection for inhibiting rotation of the elongate body within a bore in a tool holder, the radial projection being produced by forming an annular flange at or towards one end of the body and projecting radially therefrom, and removing diametrically opposed portions of the flange.

Preferably, two diametrically opposed radial projections are provided.

According to another aspect of the invention there is provided a method of producing a radial projection on an elongate body for an adjustable cutting tool, the radial projection being for inhibiting rotation of the elongate body within a bore in a tool holder, comprising forming an annular flange at or towards one end of the body and projecting radially therefrom, and removing diametrically opposed portions of the flange.

Preferably, two diametrically opposed portions of the flange are removed, which may be segments of the flange.

According to a further aspect of the invention there is provided an elongate body formed by a method according to the previous aspect of the invention and including any or none of the subfeatures mentioned in relation thereto.

An adjustable cutting tool in accordance with the invention will now be described by way of example with reference to the accompanying drawings in which:-

Fig.1 is a cross section through a tool holder showing an adjustable cutting tool in accordance with the invention mounted on one end of a tool holder and shown partly cut away, and

Fig.2 is a perspective view of one end of the adjustable cutting tool which has radial projections thereon.

A boring bar 10 is formed with an inclined bore 12. The bore 12 comprises a first section 13 terminating at a shoulder 14, a coaxial reduced diameter section 15, a larger diameter section 16 coaxial with the sections 13, 15 and a frusto-conical section 17 terminating at a face 18 at right angles to the axis of the bore 12.

A cutting tool generally indicated at 20 has a body 21 including an externally screw-threaded section 22

and a reduced diameter pilot section 23. The pilot section 23 extends between the threaded section 22 and two radially extending keys 24 on the end of the pilot section 23. The pilot section 23 fits accurately in the reduced diameter section 15 of the bore 12. The keys 24 are slidably located in respective axial key ways 31 formed in the reduced diameter bore section 15. The pilot section is formed with an internally screw-threaded bore 25 which receives a locking screw 26. The locking screw 26 has a frusto-conical head 27 which locates in a complementary recess 28 of a washer 29. The washer 29 is a clearance fit in the first bore section 13 and, as shown in Fig.1, is arranged to abut the shoulder 14.

The threaded section 22 of the cutting tool has an internally screw-threaded adjustment dial 30 thereon having a frusto-conical underside 32 which engages the frusto conical section 17 of the bore 12. The dial 30 has circumferentially spaced graduations 33 thereon which can be aligned with a single line (not shown) on the surface 18. The dial 30 has a knurled cylindrical surface 34 through which rotational force can be applied manually to the dial to enable the axial position of the cutting tool 20 in the bore 12 to be adjusted. The location of the keys 24 in the

key-ways 31 prevent rotation of the dial 30 being transmitting to the tool 20. Rotation of the dial 30 to adjust the position of the tool 20 is carried out with the locking screw 27 unscrewed so that the washer 29 disengages the shoulder 14. The dial 30 is rotated using the graduations 33 as an adjustment guide until the tool occupies the desired axial position. The locking screw 27 is then tightened to lock the washer 29 against the shoulder 14 and hold the tool rigidly in the bore 12.

The cutting end of the tool 20, either carries a brazed-on cutting tip 35 or a cutting tip or element which is clamped to the end of the tool.

During use, the dial 30 can become damaged and it is occasionally necessary to replace it. The dial 30 can be unscrewed in the direction of arrow A in Fig.1 over the cutting end of the tool and easily replaced in that manner. However, where the cutting tool includes a tip or a tip holder of a larger dimensions, e.g., as shown in broken lines indicated at 36 in Fig.1, it is impossible to unscrew the dial 30 from the cutter end of the tool. With the present invention, it will be seen that the keys 24 terminate radially inboard of the root R of the screw thread 22 by distance D. Therefore, it is possible to remove

the dial 30 from the cutting tool 20 by first detaching the locking screw 27 and withdrawing the cutting tool 20 from the bore from the direction of arrow A, and then unscrewing the dial 30 in the direction of arrow B so that it eventually disengages the screw threads 22 and can be passed over the keys 24. Once the dial has been replaced, the tool can simply be relocated in the bore 12 and easily reset before the clamping screw 27 is tightened.

The keys 24 are formed in a most advantageous manner which will now be described with particular reference to Fig.2.

When machining a metal bar to form the body 21 , the bar is first machined to provide a diameter P which corresponds to the diametral extent of the keys 24. The screw threaded section 22 and pilot section 23 are subsequently machined leaving a flange 37 at the end of the pilot section as shown in broken lines in Fig.2. The bore 26 is formed in the workpiece and screw-threaded and diametrically opposed sections 37a, 37b are machined away so as to leave two keys 24 on the end of the pilot section 23. Such a method of producing the keys is particularly straightforward

and avoids the need to provide any transverse bore and dowel, an end slot or an upset on the body to provide a key.